An orthogonal transmission scheme, such as time division and frequency division, or a space time coding (STC) scheme, such as an Alamouti scheme, can be used to avoid interference among signals transmitted to each relay station (RS). These schemes designed in a single-antenna wireless communication system are focused on improving the reliability of signal transmission using path diversity.
The use of multiple antennas leads to a sudden increase in the capacity and reliability of a wireless communication in a fading channel. Although multiple input multiple output (MIMO) technology has many merits, the chance of its realization is thin because of cost or hardware limitation. For this reason, in recent years, many researches seeking an alternative to a multiple-antenna system are in progress. With the increase of attention to a wireless network for an RS, a cooperative communication that is one of traditional technologies is emerging as an alternative for obtaining a transmission diversity gain or a multiplexing gain. Its basic idea is that a plurality of users share each other's antennas to construct a virtual MIMO channel in a dispersive scheme.
However, in the convention art, RSs have to decide to perform cooperative communication for obtaining a diversity gain or to perform cooperative communication for obtaining a multiplexing gain under the control of a base station (BS).
Thus, the conventional art has a problem in that the reliability of signal transmission increases but a spectral efficiency decreases or, inversely, a spectral efficiency increases but the reliability of signal transmission is not guaranteed.